Yardangs in Medusa Fossae

In this particular area of Medusa Fossae, the size, spacing, and orientation of the yardangs varies throughout the image. The largest form a stripe across the center of the image, while the smallest are found in the top half of the image (look closely). The small yardangs at the very top of the image are oriented NW-SE; however, the orientation changes to NE-SW near the bright ridge in the center of the image. The variation in size and orientation appears to correspond with topographic layers, and may be due either to differences in consolidation or changes in wind strength or direction as the yardangs were formed. Finally, the terrain in the lower third of the image appears etched or pitted, and was probably also formed by wind erosion.